Hidden Changes in Maine’s Ocean: A Deep Dive into Kelp Forests and Climate Impact
A conversation with Dr. Douglas Rasher
In 2018, Dr. Douglas Rasher (Bigelow Labs) was awarded $149,980 from Maine Sea Grant for a two-year project researching the return of Maine’s kelp forests with a specific focus on patterns, drivers, and implications for industry. This project is closely aligned with Maine Sea Grant’s mission to support and build a scientific research portfolio that is relevant to the issues and needs of coastal communities. It also exemplifies Maine Sea Grant’s role in supporting partnerships, providing opportunities for student engagement, and connecting science with diverse audiences. Recently, Rasher sat down with Maine Sea Grant to talk about his experience with this research and the broader implications. This conversation has been condensed and edited for clarity and length.
Kelp forests are important here in Maine and globally—they foster biodiversity in the ocean and are an important source of energy for near-shore food webs and fisheries. A recent economic analysis suggested that globally, kelp forests produce ecosystem services for humans valued at billions of dollars per year. It’s really important that we understand how these ecosystems are changing, and that we directly manage them to sustain those valuable services to our coastal economies and communities.
Our aims with this study were to try to understand how Maine’s coastal kelp forest ecosystem had changed over the past several decades, as well as urchin populations, which are intimately linked with the status of kelp and kelp forests. There hadn’t been a comprehensive survey of this ecosystem in 15 years. This was a huge surprise to us, given the importance of the ecosystem. We proposed to do a large, coast-wide survey to take the pulse of the ecosystem.
We knew from the start that a number of changes had occurred in the ecosystem. Urchin numbers were very low due to the urchin fishery in the mid-1990s. After the fishery collapsed, kelp forests rebounded coastwide. But that change dovetailed with rapid warming in the ecosystem – not only increases in average ocean temperature, but also the arrival of marine “heatwaves,” which had huge impacts on a variety of Maine’s species and habitats. We wanted to understand how these changes to fisheries and the climate were manifesting in the kelp forest ecosystem.
This research was funded in 2018 through Maine Sea Grant’s competitive research call.
Through this grant, I hired a postdoctoral scholar to collaborate on the project, and we recruited two undergraduate interns to help with the underwater survey. We also teamed up with the Maine Department of Marine Resources (DMR), which has an annual near-shore diving survey that captures information over large scales of space and time, but at coarser grain than our surveys. We aimed to blend our results with DMR’s long-term data to paint a picture of change.
What we found was alarming. While kelp forests were widespread at the turn of the century, they’ve since collapsed in the south. And although they’ve continued to persist in the north, from Penobscot Bay to the border of Canada, our northern forests have become less lush and diverse. By taking this information and constructing sophisticated models that include urchin population and ocean temperature dynamics, we then pinpointed that ocean warming was the primary driver of kelp forest decline. We also found that southern reefs, where kelp forests had collapsed, had widely become colonized by low-lying carpets of red, filamentous “turf algae.” This kelp-to-turf transition is analogous to a terrestrial forest becoming a grassy field.
This research produced several outcomes. It revealed how this iconic ecosystem is changing in light of ocean warming. It also showed that urchins remain quite rare along the outer coast of Maine, which has implications for ecosystem-based management. Last, it created opportunities to enhance the public’s engagement with science. The Sea Grant-funded research attracted the attention of National Geographic and was the impetus for follow-on work conducted at Cashes Ledge in 2023, which was funded by PBS for a nationally broadcasted NOVA special.
Our oceans are sentinels of change, but it’s hard for the average person to know what’s going on under the ocean’s surface. This ecosystem is not very accessible to scientists, let alone the public. Bringing stories from this ecosystem to the surface, to the public, is important. Sharing our observations helps to paint a picture of how warming is fundamentally changing our oceans.
Our Sea Grant award was the foundation for multiple other projects in my research program. We leveraged the data from this research to write numerous other proposals, including a large NSF grant. That funding allowed me to recruit three PhD students through the University of Maine, and we picked up where the Sea Grant project left off. That NSF project is just wrapping up now. In 2022, I went back to Maine Sea Grant seeking project development funds to start new lines of inquiry. One of my graduate students was awarded $5,000 to conduct a genetic analysis of kelp, which was the impetus for an award we received from The Nature Conservancy, allowing us to broaden our genetics work to make it coast-wide.
Overall, the 2018 Sea Grant award has reverberated to create many additional opportunities for research, student training, and public engagement. And, hopefully, it has inspired others to study this ecosystem.
I think the story in Maine can be viewed as a “glass half-empty” or a “glass half-full” situation. Yes, we have lost kelp forests in the south, and we’ve directly linked that to rapid ocean warming. This is deeply concerning. We’ve also seen that a kelp-to-turf shift is progressing up the coast, with sites changing right before our eyes. Yet, through Sea Grant funding, we’ve also documented that healthy kelp forests still exist across a vast expanse of the northern Gulf. That should be celebrated. Hopefully, our findings catalyze future science and conservation efforts in this vital habitat.
For more on Rasher’s research with kelp forests, check out:
Ocean warming undermines the recovery resilience of New England kelp forests following a fishery-induced trophic cascade Ecology, July 2024
Maine’s kelp forests, a foundation for marine life, face ‘widespread collapse’ as oceans warm – The Boston Globe, November 2024
Sea Change: Peril in the Gulf of Maine (NOVA), August 2024